For gamers the i7 and 2GB RAM.
Newer games demand more. There will never be a direct answer to your question about what occasions as the games are evolving to many core designs and starting to push up the video ram use.
My only quibble is that some folk are stunned a few years later when the unit needs repairs. These are just like high end sports cars. Repairs are a sure thing and so is the cost later.
Why a gaming laptop? Why not a desktop for that and a cheap laptop for the road?